The isothermal section of the Tb–Fe–Ga ternary system at 773 K

The isothermal section of the Tb–Fe–Ga phase diagram at 773 K was constructed by X-ray powder diffraction analysis. Four new ternary compounds, TbFe0.32Ga1.68, TbFe2.4Ga0.6, Tb4FeGa12 and TbFe5Ga7, were found in this ternary system at 773 K. The structures of the six ternary compounds, TbFe0.32Ga1.68 (InNi2-type structure, space group P63/mmc with a = 0.43727(2) and c = 0.72930(4) nm), TbFe2.4Ga0.6 (CeNi3-type structure, space group P63/mmc with a = 0. 51877(9) and c = 1.6621(4) nm), Tb4FeGa12 (U4Re7Si6-type structure, space group Im3¯m with a = 0. 85576(4) nm), Tb2FeGa8 (Ho2CoGa8-type structure, space group P4/mmm with a = 0. 4259(4) and c = 1.11356(8) nm), TbFe6Ga6 (ScFe6Ga6-type structure, space group Immm with a = 0.85551(4), b = 0.86826(5) and c = 0.50717(3) nm), and TbFe5Ga7 (ThMn12-type structure, space group I4/mmm with a = 0.86779(8) and c = 0.50923(5) nm), were determined by Rietveld refinement method.The solid solutions in this ternary system are formed by substitution of Ga for Fe. The maximum solid solubilities of Ga in TbFe2, TbFe3 and Tb2Fe17 are 19.2, 8.0, and 37.5 at.% respectively. The homogeneity ranges for the other compounds are small.